Participants eligible for a research study of the ITREL II Deep Brain Stimulation (DBS) system will have Parkinson's Disease that is poorly controlled by oral medications. The goal of this feasibility study is to determine the safety and efficacy (effectiveness) of the DBS system in controlling symptoms (difficulty in moving, walking or standing up from a chair (akinesia), uncontrolled movements of large amplitude (dyskinesias), tremor, rigidity, etc.). The device will not treat the underlying condition. The system consists of an implanted portion and an external portion. The implanted portion consists of two electrodes which are placed in the brain and connected to two temporary pulse generators. The temporary pulse generator and its connecting wire will be removed later (during internalization) and will be replaced with permanent extension wires that run under the skin to two implanted pulse generators (similar to an implantable heart pacemaker). The implanted pulse generators (IPGs) are positioned under the skin, usually below the clavicle (collarbone). The IPGs produce the electrical stimulation that is sent through the leads to the electrodes. The external portion of the system consists of a magnet that turns the IPGs on and off and allows the choice between two physician-set stimulation levels. Although the surgical operational techniques used to implant the DBS system and the DBS system itself are not experimental, bilateral deep brain stimulation for treatment of symptoms is investigational. Participation in this study will last two years.